Few Tunisians could have imagined that a president who had repressed and stifled them for more than 23 years could be so fragile, so vulnerable. As soon as the uprising that raged around the country for just over four weeks reached its capital, Tunis – with waves of protesters besieging the interior ministry, the seat of one of the region's most brutal police machines, chanting "We are free, get out!" – he fell apart like a paper tiger.

From the threatening tyrant of the early days of the rebellion, he gradually became a pale, trembling old man begging them in his televised speeches to keep him in the Carthage Palace for a little longer, first for three years, then for a mere six months. Each time Tunisians roared back from their streets "Not a day longer". Terrified, he fled the country in the dead of night. Then, rejected by France, which had clung to him until the last moment, his plane roamed around helplessly before being given permission to land in Jeddah.

The phenomenon called "Ben Ali" was in reality an amalgam of internal violence, deception and flagrant foreign support. For years his backers armed him and gave him political cover to suffocate his people. A good student of the IMF, a guarantor of "stability" and a brave warrior against "Islamic fundamentalism", Ben Ali's Tunisia was a shining example of "modernisation" and success. With his demise, a model of stability which is bought at the price of a crushed people can no longer be easily defended or propagated.

The Tunisian people's revolution, which expelled Ben Ali from their land, did not stop at their borders. It has swept over the Arab world, reverberating in every town and village. The sense of despair and profound humiliation Arabs felt with the toppling of Saddam's tyrannical regime by the US contrasts sharply with their euphoria at the ousting of Tunisia's dictator. This is the first time an Arab nation has succeeded in uprooting a ruthless despot by popular protest and civil disobedience, and without foreign intervention, coup d'etats or natural death. If Iraq offered the Arab world the ugliest face of regime change, Tunisia shows its best.

But by toppling their dictator, Tunisians are only halfway to realising their aspirations for genuine reform. The despot is gone, but the gigantic police state that has grown since the country's independence from French occupation in 1956 is still very much alive. The apparatus of repression laid down by Habib Bourguiba, Tunisia's charismatic "founding father", was fine-tuned by the general who inherited it. Dismantling such a monster will not be easy. That is the challenge Tunisians have to meet to complete their revolution.

While Arabs have been celebrating in the streets, chanting the poet Abul-Qasim al-Shabbi's words "If, one day, a people desires to live, then fate will answer their call", their rulers are stunned by the chilling news of their toppled fellow dictator. This is their worst nightmare. They dread nothing more than the Tunisian infection being passed on to their people, particularly as most have either inherited power from their fathers, or are preparing to bequeath it to their sons. Only Muammar Gaddafi of neighbouring Libya has interrupted their death-like silence to speak for all the despots, threatening Tunisians that they would live to regret what they had dared perpetrate.

But although Tunisia is a small country with a population of 10 million and scarce natural resources, it is better placed than most Arab countries to undergo democratisation. Its people are socially homogenous, largely urbanised, and highly educated compared with its neighbours. In the aftermath of Ben Ali's era, the Tunisian scene is divided between two strategies. The first involves a recycling of the old regime with a few cosmetic amendments. That is the strategy of the so-called "unity government", announced by Prime Minister Mohammed Ghannouchi today, a man who had served for years under the fallen dictator. It excludes the real forces on the ground, which genuinely reflect the Tunisian political landscape: independent socialists, Islamists and liberals. The unity government seems intent on turning the clock back, behaving as if the revolution had never been, reinstalling the loathed ruling party, the Constitutional Democratic Rally (RCD), with all the same faces – bar Ben Ali's, of course – and the same security machine. That is why protests have erupted again in many cities, with "Ben Ali out" changed to "RCD out".

The alternative strategy – and the task now facing the Tunisian people – is to build a wide coalition of the forces that can dismantle the legacy of the despotic post-colonial state and bring about the change their people have been yearning for decades. This has been the driving force for the alliance being forged between the Communist Workers' Party, led by Hamma al-Hammami, the charismatic Moncef al-Marzouqi's Congress Party for the Republic, and Ennahda, led by my father Rachid Ghannouchi, along with trade unionists, and civil society activists.

Their shared bitter experience of prison and exile has made them more pragmatic, and thus more capable of standing up to dictatorship and building a strong alliance around the demand for real change. This politics of partnership and consensus is what Tunisians and Arabs need to dismantle the structures of totalitarianism which have held them in their iron grip for generations.